The present invention relates to a novel toning agent comprising 2-hydroxynaphthalene-3,6-dicarboxylic acid and derivatives thereof. In more detail, the present invention relates to a toning agent for an azo pigment and a method for preparing an azo pigment with a modified tone.
Azo pigments are synthesized by coupling a diazonium salt with a coupler. Among the couplers employed in the coupling reaction, hydroxynaphthalene-mono-carboxylic acids and derivatives thereof are especially important compounds.
Hydroxynaphthalene mono carboxylic acids used as couplers include 2-hydroxynaphthalene-3-carboxylic acid, 2-hydroxynaphthalene-6-carboxylic acid and the like and 2-hydroxynaphthalene-3-carboxylic acid is popular.
Azo compounds synthesized with the coupler component of 2-hydroxynaphthalene-3-carboxylic acid include Brilliant Carmine 6B (Pigment Red 57) and Watchung Red (Pigment Red 48). They are prepared by diazotizing 6-amino-m-toluensulfonic acid and 6-amino-4-chloro-m-tolunensulfonic acid, respectively, and coupling the resulting diazonium salts with 2-hydroxynaphthalene-3-carboxylic acid.
In addition, an azo pigment which incorporate 2-hydroxynaphthalene-6-carboxylic acid as a coupler component has also been known (Japanese Patent Application Laid Open Nos. 302471/90 and 238231/95).
The azo pigments have been applied to various purposes, for example, printing ink, coating composition, paint composition, plastics and cosmetics. Depending on the application, a variety of performances are required for the pigment. For example, brightness and transparency are required for printing ink, durability and hiding effect are required for coating composition, and thermal resistance is required for plastics. In formulating even pigments comprising a compound having the same chemical structure, therefore, it may be necessary to formulate such pigments exhibiting properties or characteristics, which fit well with their intended application fields.
The color and other properties of a pigment are in principle the attributes of its chemical structure, but its characteristics, such as brilliance, transparency and hiding power, may change as well depending upon the physical parameters of the pigment, such as fineness, shape and surface conditions of the particles. The property of pigments can be altered to some extent by modifying the manufacturing steps, or utilizing such additives as wood rosin, for example, but cannot to a satisfactory degree. On the other hand, it is also known that the tone and physical properties of pigments can be modified by replacing a part of 2-hydroxynaphthalene-3-carboxylic acid, which is used as a coupling component, with a suitable amount of a toning agent (Japanese Patent Laid-Open No. 116753/1981). The present applicant disclosed several compounds which can modify the tone of an azo pigment (Japanese Patent Laid-Open Nos. 42662/1983, 181864/1986, 138560/1987 and 138561/1987).
Objects of the present invention are to provide a toning agent which enable to modify the tone of an azo pigment as desired, and also to provide a process for preparing an azo pigment with the modified tone.
The inventors studied intensively on toning agents which enable to modify the tone of an azo pigment as desired, and found that it could be modified by admixing 2-hydroxynaphthalene-3,6-dicarboxylic acid or a derivative thereof with the primary coupler component of the azo pigment.
Accordingly, the present invention provides a toning agent comprising a compound having the general formula [I]; 
wherein
Y is xe2x80x94(CONH)n-X or xe2x80x94COR,
Yxe2x80x2 is xe2x80x94(CONH)n-Xxe2x80x2 or xe2x80x94CORxe2x80x2,
X and Xxe2x80x2 are optionally branched alkyl groups having 1-20 carbon atoms, optionally substituted aromatic groups, or optionally substituted heterocyclic groups having conjugated double bonds,
n is an integer of 1 or 2,
R and Rxe2x80x2 are hydroxy groups, optionally branched alkoxy groups having 1-6 carbon atoms, benzyloxy groups, phenyloxy groups or phenacyloxy groups, provided that when either R or Rxe2x80x2 is a hydroxy group, said group may optionally form an acceptable salt,
R2 is a hydrogen atom, an optionally branched alkyl group having 1-6 carbon atoms, an acyl group having 1-6 carbon atoms or a phenyl alkyl group,
Z is one or more atoms or groups selected from the group consisting of a hydrogen atom, an optionally branched alkyl group having 1-6 carbon atoms, an optionally branched alkoxy group having 1-6 carbon atoms, a halogen atom, a sulfo group, a nitro group, a nitroso group, and an amino group, provided that Z may be combined with either of the two rings of the naphthalene ring.
Further, the present invention also provide a process for preparing an azo pigment comprising the steps of admixing the toning agent represented by the above formula [I] with the primary coupler component for the azo pigment and, coupling the mixed coupler composition with a diazonium salt of an aromatic compound.
The term xe2x80x9ctoningxe2x80x9d or xe2x80x9ctonexe2x80x9d as used in this invention denotes to provide pigments, by some means, with controlled properties or characteristics in terms of, for example, color, brilliance, transparency and hiding power.
The term xe2x80x9ctoning agentxe2x80x9d as used in this invention, denotes a part of coupler composition used in preparing an azo pigment. A small amount of the toning agent may be admixed with a primary coupler component used in preparation of the azo pigment to provide the pigment with a modified tone than that obtained without the toning agent. Generally, the amount of the toning agent contained in the whole coupler composition used for preparing the desired azo pigment may be less than 50 mol %, preferably less than 10 mol %, and especially, less than 5 mol %. When said amount of the toning agent is admixed with the primary coupler component, an azo pigment with a modified tone, which is different from those obtained by mixing two azo pigments, each of which is obtained by means of respective couplers (i.e. the primary coupler and the toning agent) in the ratio of the amount of the respective couplers, can be obtained.
As described above, the toning agent used in this invention, i.e. the compound represented by the general formula [I], is a 2-hydroxynaphthalene-3,6-dicarboxylic acid, or ester, amide or ureide derivative thereof.
In the present invention, the amide or ureide derivative may be prepared by obtaining acid chloride of the starting compound by means of thionyl chloride or the like in a solvent such as xylene or sulfolane in a conventional manner, and then reacting the acid chloride with amine or urea. Alternatively, they can be prepared by reacting the starting compound directly with amine or urea in the presence of phosphorous trichloride, dicyclohexylcarbodiimide or the like.
Examples of the amines or ureas, i.e. starting materials which constitutes the group X or Xxe2x80x2 in the Y and Yxe2x80x2 may include optionally branched alkyl groups having 1-20 carbon atoms, optionally substituted aromatic amino compounds such as aniline (X or Xxe2x80x2 is a phenyl group), amino naphthalene (X or Xxe2x80x2 is a naphthyl group), aminoanthracene (X or Xxe2x80x2 is a anthryl group), aminopyrene (X or Xxe2x80x2 is a pyrenyl group), amino fluorene (X or Xxe2x80x2 is a fluororenyl group) or aminoanthraquinone (X or Xxe2x80x2 is an anthraquinonyl group); and optionally substituted heterocyclic compounds having conjugated double bonds such as aminobenzimidazolone (X or Xxe2x80x2 is a benzimidazolonyl group), aminocarbazole (X or Xxe2x80x2 is a carbazolyl group), aminopyridine (X or Xxe2x80x2 is a pyridyl group), aminothiazole (X or X is a thiazolyl group), aminobenzothiazole (X or Xxe2x80x2 is a benzothiazolyl group), or aminoimidazole (X or Xxe2x80x2 is an imidazolyl group) as well as aminoindole (X or Xxe2x80x2 is an indolyl group), aminothiophene (X or Xxe2x80x2 is a thiofuryl group), aminophenothiazine (X or Xxe2x80x2 is a phenothiazinyl group), aminoacridine (X or Xxe2x80x2 is an acridinyl group), and aminoquinoline (X or Xxe2x80x2 is a quinolinyl group). Examples of the substituents include halogen atom, nitro group, lower alkyl group, lower alkoxy group, cyano group, phenyl group, morpholino group, phenoxy group, sulfo group, carboxyl group, amide group (for example, phenylaminocarbonyl group) and the like, and the phenoxy and amide groups may also have another substituent such as halogen atom, lower alkyl group, lower alkoxy group, alkylaminosulfonyl group, nitrile group or the like.
By reacting the above described amino compound and potassium cyanate, a corresponding urea can be obtained. That is, phenyl urea, for example, can be obtained from aniline.
Y or Yxe2x80x2 may represent xe2x80x94COR or xe2x80x94CORxe2x80x2. When either R or Rxe2x80x2 is a hydroxy group, it may form an alkaline metal salt. Examples of the alkaline metals include sodium, potassium, lithium and the like. When R is xe2x80x94OR1 or Rxe2x80x2 is xe2x80x94OR1xe2x80x2, R1 or R1xe2x80x2 is an optionally branched alkyl group having 1-6, preferably 1-4 carbon atoms, a phenyl group, a benzyl group, or a phenacyl group, each of the groups may be substituted.
Preferably, at least one of Y and Yxe2x80x2 is carboxylic acid (xe2x80x94COOH).
R2 is a hydrogen atom, an optionally branched alkyl group having 1-6, preferably 1-4 carbon atoms, especially, methyl or ethyl group; an acyl group having 1-6, preferably 1-4 carbon atoms, especially acetyl group; or a phenylalkyl group wherein the phenylalkyl group may have a substituent such as a halogen atom or a lower alkyl group.
The compound of the formula [I] used as a toning agent of the present invention may be prepared in a manner described in WO96/32366 and WO98/16513.
The process of the present invention for preparing an azo pigment with a modified tone may be conducted by admixing the toning agent of the formula [1] with the primary coupler component for the azo pigment, and coupling the obtained mixed coupler composition with a diazonium salt of an aromatic compound, which is obtained by diazotizing an aromatic amine.
Examples of the aromatic amines include aniline, monoamino condensed polycyclic hydrocarbons such as naphthylamine, monoaminoanthracene, monoaminoindene, and monoaminofluorenone, as well as monoaminoindole, monoaminobenzothiophene, monoaminoquinoline, and monoaminocarbazole. The above-described aromatic amines may have a substituent. Examples of the substituents include halogen atom, lower alkyl group, especially methyl, halogenated lower alkyl group, cyano group, nitro group, lower alkoxy group, amide group, sulfo group, alkylamino sulfonyl group, aminocarbonyl group, phenylaminocarbonyl group, phenoxy group, alkoxycarbonyl group, hydroxy group, benzoylamino group, toluidylamino group, triazylamino group, and pyrimidylamino group.
The azo pigment obtained by the present invention may be used for preparing a lake pigment. Agents which is used to make the lake pigment may include Ca salt, Ba salt, Sr salt and Mn salt. The lake pigment may be prepared in a conventional manner.
The amount of the compound of formula [I] in the coupler composition is not limited. However, too much toning agent will provide a color completely different from the original color of the pigment, and therefore, the amount of the toning agent in the whole coupling composition may generally be less than 50 mol %, preferably, 0.1-10 mol %, especially, 0.2-5.0 mol %.
The primary coupler component of the present invention may be any as far as different from the compound represented by the formula [I]. Examples of the coupler component include naphthols such as xcex1-naphthol and xcex2-naphthol, hydroxynaphthalene monocarboxylic acids or derivatives thereof. Preferable couplers are hydroxynaphthalene monocarboxylic acids and derivatives thereof, for example, 2-hydroxynaphthalene-3-carboxylic acid, 2-hydroxynaphthalene-6-carboxylic acid, or esters or amides thereof.
Examples of the esters include alkyl esters such as methyl, ethyl, and propyl, phenyl ester, benzyl ester, phenacyl ester and the like and each of the ester groups may have a substituent.
Examples of the amides include aromatic amide which may optionally form a heterocyclic group, such as phenylamide, xcex1- or xcex2-napthylamide, anthraquinonylamide, benzimidazolonylamide, carbazolylamide, pyridylamide, thiazolylamide, benzothiazolylamide, imidazolylamide, indolylamide, thiofurylamide, phenothiazinylamide, acridinyl amide and quinolinylamide. Each of these amide groups may have a substituent, for example, halogen atom, nitro group, lower alkyl group, lower alkoxy group, cyano group, phenoxy group, amino group such as methylcarbonylamino group.
The process for preparing a diazonium salt from an amine is not limited. A conventional method comprising the step of diazotizing an amine with sodium nitrite may be employed.
According to the present invention, by admixing one or more compounds of the formula [I] with the primary coupler component, the crystal growth of the azo pigment synthesized with the mixed coupler composition is effected to provide a modified pigment with a modified color, tone and/or transparency.
The toning effects may vary widely depending on the kind of the diazonium compound used, or with the kind and amount of the compound of the formula [I] used.